Doherty amplifiers are amplifiers commonly used in wireless communication systems. Today, for example, Doherty amplifiers are used increasingly in base stations that enable the operation of wireless communications networks. Doherty amplifiers are suitable for use in such applications because the amplifiers include separate amplification paths, typically a main or carrier path and a peaking path. The two paths are configured to operate at different classes. More particularly, the main amplification path typically operates in a class AB mode and the peaking amplification path is biased such that it operates in a class C mode. This enables improved power-added efficiency and linearity of the amplifier, as compared to a balanced amplifier, at the power levels commonly encountered in wireless communications applications.
Although the Doherty amplifier architecture presents several benefits over other amplifier configurations, a Doherty amplifier must often be augmented with some form of linearity enhancement when used in high-power base station transmitter systems. In many cases, digital predistortion (DPD) is utilized to improve the linear performance of the amplifier for wireless infrastructure applications. Unfortunately, the utilization of DPD correction techniques requires additional hardware and software, consuming additional power and thereby lowering transmitter efficiency. Additionally, the efficacy of DPD correction is affected by non-linear mechanisms occurring within the power amplifier itself. These non-linear mechanisms can be difficult to control, particularly in a lineup amplifier configuration that includes a dual-path Doherty architecture.